Study the graph given below and answer the questions that follow :
(i) Write the status of food and space in the curves a and b.
(ii) In the absence of predators, which one of the two curves would appropriately depict the prey population ?
(iii) 'Time' has been shown on x-axis and there is a parallel dotted line above it. Give the significance of this dotted line.
Show Hint
Curve a is exponential growth with unlimited resources and curve b is logistic growth with limited resources. The dotted line is the carrying capacity K.
Step 1: Read the graph:
The graph plots population density (N) against time (t). Curve a rises steeper and steeper without levelling off.
Curve b is S-shaped (sigmoid). It rises slowly, then fast, and finally flattens at the dotted line.
Step 2: Part (i), status of food and space:
Curve a is exponential growth. This happens only when food and space are unlimited, so they are in plenty.
Curve b is logistic growth. Food and space are limited, so growth slows and stops.
Step 3: Part (ii), prey without predators:
Predators keep prey numbers in check. If they are absent, nothing removes the prey.
The prey would multiply freely, as in curve a. So curve a would depict the prey population.
Step 4: Part (iii), the dotted line:
In curve b the population levels off at the dotted line. This line marks the carrying capacity (K).
Carrying capacity is the maximum population that the environment can support with its available resources.
Final Answer:
(i) a: food and space unlimited; b: food and space limited. (ii) Curve a. (iii) The dotted line shows the carrying capacity K of the environment.
